It will visit Laganside Courts, where the groups will openly challenge the law by supplying abortion pills to women here.

It will then travel to the constituency offices of prominent pro-life DUP, Sinn Fein, UUP and SDLP representatives including Edwin Poots, Francie Molloy and Patsy McGlone, where activists will stage a protest.

The pills will be delivered by a remote control robot outside the court at noon.

A doctor will counsel women remotely, as the robots are operated from the Netherlands in a bid to avoid breaking the law.

The day will end with a rally in Londonderry attended by pro-choice activists and trade unionists.

Eleanor Crossey-Malone of Rosa NI said the event would begin with five activists - who will not disclose whether they are pregnant - taking the pills.

Other women seeking the tablets - misoprostol and mifepristone - would then be able to obtain them from the bus under medical supervision.

Last night PSNI detective chief superintendent Tim Mairs said it would investigate any suspected criminal offences.

"Offences of procurement of an abortion are outlined in Sections 58 & 59 of the Offences against the Person Act 1861 and Child Destruction Sect 25 (1) Criminal Justice (NI) Act," he said.

"These offences can reasonably be suspected in circumstances where individuals receive or procure prescription medications which are known to be used or advertised as suitable for inducing an abortion.

"Ingesting such drugs when pregnant or ordering and providing them to another person who is pregnant may constitute a criminal offence.

"Where we have reasonable grounds to suspect any offence has been committed or attempted, the PSNI is obliged under Section 32 of the Police Act 2000 to take measures to bring the offender to justice.

"Where the PSNI is made aware of any suspected offences, each case will be investigated on its own merits.

"The issue of abortion is clearly a very emotive and sensitive issue that divides opinion." Meanwhile, one of Ireland's most high-profile priests said a couple's support for abortion would not necessarily preclude him from officiating at their marriage in a Catholic church.

It comes after outspoken Belfast cleric Fr Patrick McCafferty said those who don't agree with Catholic teaching on abortion should "get married in City Hall" rather than being "hypocritical and dishonest by using the Church for a day".

However, Co Down Passionist priest and well-known broadcaster Fr Brian D'Arcy said: "Why should it? If they're willing to ask for a Catholic marriage and have the sincerity to do that then I'd do my best to reciprocate."

But he added: "I'm not going to give a yes or no answer because it isn't a yes or no question. Each person is different, each case is different."

Rosa NI, which has widely advertised the Bus4Choice's visit to Belfast on social media, described abortion law here as "draconian" and "archaic." It said today's event will "flout Northern Ireland's abortion laws in the wake of the repeal referendum in the south".

Abortion can only be accessed in Northern Ireland when a woman's life is at risk, or there is a "real and serious adverse effect on her physical or mental health which is long-term or permanent".

On March 8, 2017 the PSNI seized more than 100 packets of abortion pills in two raids. It was International Women's Day.

The seized mifepristone and misoprostol tablets induce abortion and were ordered online by women who could not afford to travel to England to procure a legal termination. Ms Crossey-Malone said: "It's a point of principle that we won't reveal whether or not the activists are pregnant.

"We don't believe it's anybody else's business, and they should be able to decide what happens to their own bodies.

"These pills are in the World Health Organisation's list of essential medicines; they haven't been bought from a drug store and they will be prescribed by a doctor.

"I would say that it is unlikely that the PSNI will arrest us.

"We think it's extremely unlikely that we will go to jail.

"We understand that what we are doing is civil disobedience, and there is a risk, but it's something we absolutely need to do to get change. We are willing to take the risk of jail.

"We have a situation where women seeking abortion services which are available in the rest of the UK must either travel, if they can afford it, or risk breaking the law by taking these pills.

"The purpose of this event is to bring the taking of these pills out of the dark and put it in the public eye."

However, Life NI's Marion Woods, whose group is part of the Both Lives Matter campaign, criticised the planned event.

She said: "The whole point of this is it's a stunt to make the law unworkable.

"I think it's very unfair. It feels very much like playground bullying. They are obviously looking for a reaction.

"There was a similar stunt with a drone in 2016.

"We are concerned at the impact it will have on women.

"This is a stunt, a tactic, trying to flout the law of the land."

She added: "It is for the PSNI to decide if the law has been broken and if action is taken."

Women on Waves said: "With the robot, the abortion pills can be supplied to women in Northern Ireland without breaking the law because the robot is operated from the Netherlands.

"Although the women in Northern Ireland would break the law if they were pregnant while taking the abortion pills, this is a matter of patient confidentiality and forcing women to undergo a pregnancy test would be a severe violation of their human rights."

Last year an unnamed man and woman accused of attempting to procure an abortion in Belfast accepted formal cautions.

Also, last January, a mum who helped her 15-year-old daughter buy abortion pills online won the right to contest the decision to prosecute her.

Two years ago a young woman who bought drugs on the internet to induce a miscarriage after failing to raise enough money to travel to England for a termination was handed a suspended prison sentence.

The 21-year old miscarried on July 12, 2014, after taking two types of drugs she had bought online.

The foetus, which was between 10 and 12 weeks, was later found in the bin of a house that she shared with two other people.